telemere/wiki/3-Config.md

See below for config by topic-

Filtering

A signal will be provided to a handler iff ALL of the following are true:

• 1. Signal creation is allowed by signal filters:
  • a. Compile time: sample rate, kind, ns, id, level, when form, rate limit
  • b. Runtime: sample rate, kind, ns, id, level, when form, rate limit
• 2. Signal handling is allowed by handler filters:
  • a. Compile time: not applicable
  • b. Runtime: sample rate, kind, ns, id, level, when fn, rate limit
• 3. Signal middleware (fn [signal]) => ?modified-signal does not return nil
• 4. Handler middleware (fn [signal]) => ?modified-signal does not return nil

See help:filters for more about filtering.

Signal handlers

See section 4-Handlers.

Interop

tools.logging

tools.logging can use Telemere as its logging implementation (backend).

To do this:

1. Ensure that you have the tools.logging dependency, and
2. Call tools-logging->telemere!, or set the relevant environmental config as described in its docstring.

Verify successful intake with check-intakes:

(check-intakes) ; =>
{:tools-logging {:sending->telemere? true, :telemere-receiving? true}}

Java logging

SLF4J can use Telemere as its logging backend.

To do this, ensure that you have the following dependencies:

[org.slf4j/slf4j-api          "x.y.z"] ; >= 2.0.0 only!
[com.taoensso/slf4j-telemere  "x.y.z"]

Telemere needs SLF4J API version 2 or newer. If you're seeing Failed to load class "org.slf4j.impl.StaticLoggerBinder" it could be that your project is importing the older v1 API, check with lein deps :tree or equivalent.

When com.taoensso/slf4j-telemere is on your classpath AND no other SLF4J backends are, SLF4J will direct all its logging calls to Telemere.

Verify successful intake with check-intakes:

(check-intakes) ; =>
{:slf4j {:sending->telemere? true, :telemere-receiving? true}}

For other (non-SLF4J) logging like Log4j, java.util.logging (JUL), and Apache Commons Logging (JCL), use an appropriate SLF4J bridge and the normal SLF4J config as above.

In this case logging will be forwarded:

1. From Log4j/JUL/JCL/etc. to SLF4J, and
2. From SLF4J to Telemere

System streams

The JVM's System/out and/or System/err streams can be set to flush to Telemere signals.

To do this, call streams->telemere!.

Note that Clojure's *out*, *err* are not necessarily automatically affected.

Verify successful intake with check-intakes:

(check-intakes) ; =>
{:system/out {:sending->telemere? true, :telemere-receiving? true}
 :system/err {:sending->telemere? true, :telemere-receiving? true}}

OpenTelemetry

OpenTelemetry interop is experimental - feedback very welcome!

Telemere can send signals as correlated LogRecords and tracing data to configured JVM OpenTelemetry exporters.

To do this:

1. Ensure that you have the OpenTelemetry Java dependency.
2. Ensure that OpenTelemetry Java and relevant exporters are appropriately configured.
3. Use handler:open-telemetry-logger to create an appropriately configured handler, and register it with add-handler!.

Once registered, this handler will automatically process relevant Telemere signals to emit detailed log and trace data to your OpenTelemetry exporters.

Note that aside from configuring the exporters, Telemere's OpenTelemetry interop does not require any use of or familiarity with the OpenTelemetry Java API or concepts. Just use Telemere as you normally would.

Tufte

Tufte is a simple performance monitoring library for Clojure/Script by the author of Telemere.

Telemere can easily incorporate Tufte performance data in its signals, just like any other data:

(let [[_ perf-data] (tufte/profiled <opts> <form>)]
  (t/log! "Performance data" {:perf-data perf-data}))

Telemere and Tufte work great together:

• Their functionality is complementary.
• The upcoming Tufte v4 will share the same core as Telemere and offer an identical API for managing filters and handlers.

Truss

Truss is an assertions micro-library for Clojure/Script by the author of Telemere.

Telemere can easily incorporate Truss assertion failure information in its signals, just like any other (error) data.

The catch->error! signal creator can be particularly convenient for this:

(t/catch->error! <form-with-truss-assertion/s>)